1. Field of the Invention
The present invention relates to an apparatus for manufacturing a single silicon crystal by the use of the Czochralski process, and more particularly, to an apparatus for pulling a single silicon crystal while continuously feeding silicon materials.
2. Description of the Prior Arts
A method for pulling a single silicon crystal by the use of the Czochralski process has previously been used and this method is a substantially completed technique. However, the yield of wafers being able to stand their use can be 50% or less due to maldistribution of dopants and oxygen in case requirements of components are severe.
As an effective method for solving the foregoing problem, there is known a method wherein a liquid surface of molten materials is maintained at a predetermined level by continuously or intermittently replenishing a crucible with silicon material. Particularly recently, high-quality granular polycrystal silicon has come to be able to be manufactured, and several inventions wherein this high-quality granular polycrystal silicon is used are disclosed. Those inventions are, for example, disclosed in Japanese Patent Publications Laid Open No. 130195/83 and No. 95195/88 and in Japanese Utility Model Publication Laid Open No. 141578/84.
Only one or two examples of having manufactured single silicon crystal of a small diameter are seen in the method for manufacturing a single silicon crystal by the use of the foregoing method, but micro defects or the like in the single silicon crystal are not described.
It is understood that there are the following problems in the prior art apparatus for pulling a single silicon crystal while continuously and directly replenishing a crucible with granular silicon when there is used a transparent quartz glass usually used for manufacturing semiconductor materials as a partition member partitioning molten silicon materials in the crucible into a single crystal growing portion on the inner side and a material melting portion on the outer side.
(1) Even though a single silicon crystal is made to grow rapidly so that micro defects can be hard to be incorporated into the single silicon crystal, there occur a great amount of oxidation-induced stacking faults (OSF) in comparison with the conventional Czochralski process.
(2) A vibration of the surface of molten silicon is large and this hinders crystallization of the molten silicon.